In a typical dual channel weather radar system, a transmission signal is generated in an amplifier or a power oscillator, then passed through waveguides, rotary couplers and possibly transmitters and power dividers before being transmitted from an orthogonal feedhorn and antenna into the atmosphere. When a reflected signal is received, the reflected signal is compared to the signal generated by the amplifier or oscillator to determine weather conditions. The power and phase of the signal, relative to the transmitted signal, are important in determining the weather characteristics. Thus, having an accurate depiction of the transmitted signal is necessary in forming an accurate picture of the weather conditions.
Components in a weather radar system may introduce delays in the signal (thus shifting the phase of the signal) and may also lose power from the signal prior to transmission. For example, as the signal is passed across rotary couplers in the transmission path to the antenna, some of the signal may be lost in the coupling, and may be delayed so that the phase and power of the signal changes after it passes through the coupling. Thus, any comparison of the transmitted signal to the received signal is more accurate if the comparison includes the delay and power loss through the coupler.
In single polarized signals, any shift in phase is not as important because the return transmission time, i.e., the reception interval, is much greater than any shift in phase created by the components in the system prior to transmission. However, in a dual channel weather system, a change in phase of the signal on one of the channels relative to the signal of the other channel introduces additional error because the analysis of a dual channel weather system includes analysis of the two received signals relative to each other. Thus, any change in phase due to delays within the system may effect the analysis of the signals.
Moreover, any delays in the system or loss in signal power also effects the range of the signal. If delays in the signal are present, then the interval between signals must be longer to allow for the delay. In order to maintain the same interval, then the range would effectively be limited by the delay, or estimated delay. In addition, the maximum range is proportional to the transmitted power raised to the ¼ power. Thus, signal delays and power loss may limit the range. Such delays may be minimized by a system that can accurately determine when components are causing delays and losses for replacement of components.